How can one tell from the appearance whether a regulator is positive-acting or negative-acting?
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How can one tell from the appearance whether a regulator is positive-acting or negative-acting? For a regulator that is currently in operation, I want to know whether it is positive-acting or negative-acting From which aspects should one look for it?
We choose positive-acting regulators for all of them, as it’s more convenient.
Observe whether the current deviation is positive or negative; it is the measured value minus the given value, and a positive value indicates a positive deviation； The same is true in reverse. Observing the output of the regulator, it shows an increasing trend over a period of time, that is, the output increases. Positive deviation + increased output = positive action ； The same is true in reverse
Positive action – refers to the situation where the output of the regulator increases as the positive deviation increases (that is, when the measured value is greater than the set value); in other words, the regulator’s output rises as the measured value increases. Backaction – refers to the situation where the output of the regulator decreases as the positive deviation increases; in other words, the regulator’s output declines as the measured value rises. Last edited by XJTZWKDPJ on 2007-12-29 at 20:04.]
I misunderstood the original poster’s intention and misled everyone. I thought it was an electrical valve positioner!
For diaphragm control valves, check whether the pneumatic signal tube located on the diaphragm head is in the upper or lower part of the head. In general, control valve seats operate in a direct-acting manner; thus, if the pneumatic signal tube is in the upper part of the diaphragm head, it is a direct-acting valve, while if it is in the lower part, it is an inverse-acting valve.
I agree with what was said on the third floor; introducing the forward and reverse actions of the control valve upstairs can easily confuse beginners.
The regulator is the correction unit of an automatic control system, and it offers two operating directions, positive and negative, for selection. From the perspectives of process and equipment safety, the direction of its action can generally be determined by inferring from the system’s negative feedback control logic. The positive and negative actions of the regulator are defined as follows: the error signal e = measured value C – setpoint value r (which is exactly the opposite of what is specified for control systems). When e>0, the regulator output m increases in a positive manner ； When e
I feel that what the original poster wants to ask is how to determine whether the actuator of a control valve operates in forward or reverse mode on-site, rather than regarding the regulator